Numerical simulations based on the three-dimensional discrete element method (DEM) are carried out for studying the mixing behavior of monocomponent and binary particle systems in a spouted bed. The motion of individual particles is modeled by DEM, and the gas motion is modeled by the k - epsilon two equation turbulent model. The mixing quality is described by the Lacey mixing index, it is evaluated in terms of the mixing degree at the mixing equilibrium and the time required reaching the steady value. The state of mixing of uniform particles is studied by analyzing the effect of particle shape, density and spouting gas velocity. For binary systems, the effects of component shape and size are examined. The results show that spouting gas velocity and particle properties are important parameters influencing particle mixing quality in spouted bed. The mixing quality is found to be sensitive to particle shape, the spheres mix faster and more homogeneous than corns. In monocomponent corn system, the mixing quality increases with increasing of gas velocity and decrease with increasing particle density, and it is sensitive to particle shapes, the spheres mix faster and more homogeneous than corns. In binary corn-sphere system, particles with closer sizes and operated at higher gas velocity have better mixing quality. Besides, the mixing mechanism of corn-shaped particles is discussed based on the mixing process of monocomponent and binary systems. It is found that particles of different shapes, sizes and densities can have different trajectories in the fountain region, leads to a different radial landing position on the top of the annulus, and the subsequent path through the annulus region varies. (C) 2012 Elsevier B.V. All rights reserved.